A boy on the throne of Amer
His house: the Kachwahas had ruled from Amer for centuries and had been the Mughals' closest Rajput allies since Raja Bharmal's alliance with Akbar in 1562.
His inheritance: a hill fort, a proud name and a duty of service to the emperor. Kachwaha princes had commanded Mughal armies from Kabul to Bengal.
- Born
- 1688
- Came to the throne
- 1699, aged about eleven
- Capital
- Amer, in the hills north of Jaipur
- Clan
- Kachwaha Rajputs
- Died
- 1743
- His name: Jai Singh, victory lion. He was the second of the name, so historians call him Jai Singh II.
- The title Sawai: sawai means one and a quarter. By tradition the Mughal court gave it to him as a compliment, meaning he was worth more than one ordinary man. Jaipur's rulers have used it ever since.
- A divided empire: after Aurangzeb died in 1707, his sons and grandsons fought over the throne. A young king in Amer had to pick sides carefully, and Jai Singh once lost Amer for a time for picking the wrong one.
- He won it back: with Rathore allies from Marwar he recovered his capital, and he spent the next three decades as one of the most trusted men at the Mughal court.
- An early education: he learned Sanskrit, Persian and mathematics as a boy. The astronomy came from that schooling, and from a lifelong habit of asking why the books disagreed.
General, governor and diplomat
Governor of provinces: he was posted as governor of Malwa and of Agra at different times. Each post brought revenue, soldiers and influence.
A negotiator in a rough age: the Marathas were pushing north and the Jats of Bharatpur were rising. Jai Singh fought some and bargained with others, and he was often the emperor's go-between.
- The emperor he served longest: Muhammad Shah, who ruled from 1719 to 1748. Jai Singh dedicated his great star tables to him.
- Why service mattered: imperial posts paid for Jaipur. The wealth from Mughal service built the palaces, the walls and the observatories.
- Rajput politics at home: he married into other Rajput houses, mediated their quarrels and tried to keep a league of Rajput kings together as Mughal power faded.
- A builder of forts: the hill forts above Jaipur were part of his defence. The great cannon called Jaivana was cast at Jaigarh Fort in his reign, and Nahargarh was begun near its end.
- A Hindu king in a Mughal world: he was a devout patron of temples and Sanskrit learning, and tradition says he performed the ancient horse sacrifice, the ashvamedha, as a statement of royal power.
Why a king took up astronomy
The everyday reason: the panchang, the Hindu almanac, sets the dates of festivals and the right hours for weddings. If the tables are wrong, the whole calendar of life is wrong.
The scholar's reason: he read the Sanskrit astronomical texts and the Persian and Arabic tables of the Islamic astronomers, and found that none matched what he could see.
- The problem
- Calendars and eclipse predictions had drifted
- His sources
- Sanskrit, Persian, Arabic and European works
- His method
- Build bigger instruments, measure again
- His aim
- Accurate tables for time, eclipses and festivals
- The famous models: he knew of the observatory of Ulugh Beg at Samarkand, built in the fifteenth century, with its giant masonry arc. That idea of building in stone shaped everything he did.
- A small instrument problem: brass astrolabes are beautiful but small. A small scale can only be read so finely, and metal bends, wears and shifts.
- His answer: build the instruments in masonry, at the size of houses, so that a degree becomes a hand's breadth and a minute of time becomes something you can watch.
- Repeat and compare: his observers took the same readings again and again and checked them against each other. It was slow, careful, team work.
- The shared sky: like the astronomers he admired, he combined traditions. Sanskrit names, Persian tables and European ideas met in one courtyard.
Five observatories, from Delhi to Varanasi
Delhi, the first
Built: the 1720s, in the imperial capital, near what is now Connaught Place.
- What survives: a great sundial and a handful of large instruments in a small park among office blocks.
- Why see it: it is where the experiment began, close to the court that paid for it. Our Delhi guide fits it into a morning.
Jaipur, the greatest
Built: instruments were standing by 1728, and the observatory was substantially complete in 1734.
- What survives: nineteen instruments, including the Vrihat Samrat Yantra, about 27 metres tall, the largest stone sundial in the world.
- Why see it: it is the largest, the best kept and the only one inscribed by UNESCO. Read our full Jantar Mantar guide.
Ujjain, the old meridian
Why Ujjain: Indian astronomers had long used Ujjain as their prime meridian, the line from which longitude was counted, so it was a natural place to measure.
- What survives: a smaller observatory with a sundial and several instruments, still used to teach astronomy.
- Getting there: Ujjain is in Madhya Pradesh, best combined with a journey through central India rather than Rajasthan.
Varanasi, on a palace roof
Where: on the roof of the Man Mandir, a riverside palace built around 1600 by Raja Man Singh I of Amer, Jai Singh's great ancestor.
- What survives: a compact set of instruments with a wide view over the ghats and the Ganga.
- Why see it: it ties the Kachwahas of Rajasthan to the holiest city in India. Our Varanasi guide shows how to reach it from the river.
Mathura, the lost one
- What happened: the observatory at Mathura was dismantled in the nineteenth century and nothing of it survives.
- Why it matters: it reminds us that these were working tools, not monuments, and that their survival was never certain.
Inside the Jantar Mantar at Jaipur
Vrihat Samrat Yantra: the supreme sundial. Its shadow moves about a millimetre a second across the marble, fast enough to watch with your own eyes.
Laghu Samrat Yantra: the small sundial, accurate to about twenty seconds. Learn to read it first, and the big one makes sense.
- Instruments
- Nineteen, in stone, marble and bronze
- Largest
- Vrihat Samrat Yantra, about 27 metres
- Accuracy
- The big sundial reads to about two seconds
- Best hour
- Late morning, in full sunshine
- Allow
- About ninety minutes with a guide
- Jai Prakash Yantra: two sunken bowls that mirror the sky. A small ring strung above casts a dot of light that marks the sun's position. It is said to be his own design.
- Rashivalaya Yantras: twelve instruments, one for each sign of the zodiac. Children love finding their own.
- The great bronze astrolabe: about 2.4 metres across, a reminder that he kept using metal instruments where they served him best.
- Local time, not clock time: the sundials show solar time over Jaipur, so they run about twenty-seven minutes behind Indian Standard Time, before the seasonal correction.
- Aligned to the pole: the slope of the great sundial is set to Jaipur's latitude, about 27 degrees, so it points to the pole star.
The scholars around the king
Jagannatha Samrat: his court scholar, who translated Ptolemy's Almagest and Euclid's Elements into Sanskrit. The Euclid translation is known as the Rekhaganita.
Vidyadhar Bhattacharya: the Bengali scholar and architect who helped plan Jaipur itself, and whom the city still honours as its planner.
- The Zij-i Muhammad Shahi: Jai Singh's star tables in Persian, dedicated to the emperor. They were used across India for about a century.
- A Sanskrit treatise: a work on the astrolabe, the Yantraraja, is credited to his circle and shows how seriously he studied the instruments he later outgrew.
- European contact: he knew Jesuit scholars in India and is said to have sent a mission to Portugal for European tables. He compared them with his own and found they disagreed too.
- More than twenty astronomers: at its height the Jaipur observatory employed a team of observers who took readings by day and by night.
- The language of the walls: look closely at the scales and you will see Sanskrit and Persian numerals side by side. The bilingual court is written into the stone.
A city laid out like a diagram
Founded in 1727: Jai Singh moved his capital down from the cramped hills of Amer to the plain, where there was room for water, trade and a city of his own design.
Nine blocks: the plan follows the old Indian building texts, with the city divided into a grid of large blocks. The palace and the observatory sit at the centre.
- Broad, straight bazaars: the main streets run east to west and north to south, wide enough for processions and lined with shops of matching height.
- Planned by trade: jewellers, metalworkers and cloth merchants were each given their own streets, which is why Jaipur's bazaars still sort themselves by craft.
- The palace at the heart: the City Palace, begun in 1729, sits beside the Jantar Mantar. The king could walk from his rooms to his instruments.
- The pink came later: the city was colour-washed in pink in the nineteenth century, long after Jai Singh. Our piece on why Jaipur is pink tells that story.
- UNESCO again: the walled city itself was inscribed as a World Heritage Site in 2019, partly for the plan Jai Singh drew.
What happened after he died
A disputed succession: his sons fought over the throne after his death, and the long peace he had bought for Jaipur came to an end.
The tower of victory: one son, Ishwari Singh, raised the Isarlat, the tall tower near Tripolia Bazaar, to mark a battle in that struggle. You can climb it for a view over the walled city.
- His death
- 1743
- Repaired
- 1876, under Sawai Ram Singh II
- Restored
- 1901, under Sawai Madho Singh II
- National monument
- 1948
- UNESCO
- 2010
- Neglect: wars, debts and Maratha demands left little money for astronomy, and the instruments weathered for long stretches.
- The first repair: Sawai Ram Singh II, the moderniser who painted the city pink, had the instruments repaired in 1876.
- The big restoration: in 1901 Sawai Madho Singh II ordered a thorough restoration supervised by Major Arthur Garrett, an engineer and amateur astronomer. Some marble scales date from that work.
- Protection: after independence the observatory became a national monument in 1948, and UNESCO inscribed it in 2010.
- Was it good science? historians still debate how much new data the instruments produced. Nobody disputes that they are the finest surviving monument of naked-eye astronomy anywhere.
A day in Jai Singh's Jaipur
Early morning at Amer
- Why first: Amber Fort at opening time, before the crowds, to see the hill palace where his story began.
- Look for: the views down to Maota Lake and the narrow valley the Kachwahas guarded for centuries.
Late morning at the Jantar Mantar
- Why then: the shadows are sharpest when the sun is high, so the sundials work best between late morning and early afternoon.
- With a guide: ask them to read the Samrat Yantra for you and do the time correction on the spot.
Afternoon in the City Palace
- What to see: the museum courts, the painted gates of Pritam Niwas Chowk and the portraits of the Kachwaha rulers.
- Look for: a portrait of Jai Singh himself among his descendants. Our piece on the Jaipur royal family explains who is who.
Sunset at Nahargarh
- Why end here: the fort begun in his last years gives the best view of the grid he drew.
- Then: dinner back in town, perhaps at Rambagh Palace, and an early night if you want the stars.
What most visitors miss
The moving shadow: stand at the scale of the big sundial, pick a mark and wait a minute. Watching the shadow slide past it is the whole point.
The numerals: find a spot where Sanskrit and Persian numbers sit together on the same scale.
- Old and new stone: sharp-eyed guides can show you where the 1901 marble meets the older work.
- The alignment: stand at the foot of the great gnomon and look up its slope. You are looking along a line that points to the pole.
- The Isarlat: few visitors climb the tower of Jai Singh's son. The view over the grid of the old city is one of the best in Jaipur.
- The palace window: from parts of the City Palace you can see the observatory below. It shows how close the king kept his science.
Before you go
Choose a sunny day: the sundials need sharp shadows. On a hazy or cloudy morning, move the visit to the next day if your plan allows.
Go between October and March: the courtyard has little shade, and in the hot months the stone throws back the heat. In summer, come at opening time and keep it short.
- Bring a hat and water: you will spend most of the visit in full sun, looking up.
- Book a guide who knows the science: the instruments only come alive when someone shows you how to read them. We use guides who can do the time correction in their heads.
- Read one page first: our history of Rajasthan gives the Mughal background in ten minutes, and makes his career far easier to follow.
- Keep off the instruments: climbing on them is not allowed, and the marble scales are fragile. Watch children near the steps of the big sundial.
Who will love this story
Families: children love the moving shadow and the zodiac instruments, and the science gives the history a hook.
Engineers and scientists: you will enjoy arguing about accuracy and method with a guide who knows the instruments well.
- Good for
- Curious minds, families, engineers, teachers
- Time needed
- A full day in Jaipur
- Best months
- October to March
- Pairs with
- Delhi, Varanasi, a night of stargazing
- History lovers: he is a window on the Mughal court in decline, seen through a Rajput who thrived in it.
- Repeat visitors: if you have seen Jaipur's palaces, a day built around Jai Singh shows you the city in a new way.
- Planning a longer trip: our Jaipur itinerary and the Jaipur in three nights journey make room for a full day of his story.